Arizona-based semiconductor maker Versum Materials, Inc. announced on Monday that Merck KGaA increased its bid to buy the company for for $53 per share, noting the new bid by the German pharmaceutical giant represents a "superior proposal" to the previously agreed all-stock merger with Entegris, Inc.

"On April 7, 2019, Versum notified Entegris that Versum had received the revised proposal from Merck, that Versum’s Board of Directors has unanimously determined that Merck’s proposal constitutes a “Superior Proposal,” and that Versum’s Board of Directors intends to terminate the Entegris merger agreement to enter into a definitive merger agreement with respect to Merck’s proposal," Versum stated. "Entegris has the right, during the four business day period ending on April 11, 2019, to propose revisions to the existing merger agreement between Versum and Entegris," the company added.

In March, Versum rejected Merck's unsolicited cash offer of $5.9 billion, or $48 per share, after accepting a $4 billion bid from Entegris a month earlier.